Identify the dense aponeurotic linea alba (white line) that runs vertically from the xiphoid process to the pubic symphysis. This line represents the midline convergence of aponeuroses of three abdominal muscles at the midline.

Lateral to the rectus abdominis muscle on each side, identify the linea semilunaris . These paired and slightly curved vertical lines represent the lateral border of the rectus sheaths which enclose the rectus abdominis muscle on each side.